1. Field of the Invention
The present invention generally relates to a wafer storage container used for storage, shipping, archiving, or the like of a precision wafer such as a semiconductor wafer.
2. Background Art
A wafer storage container for storage of a semiconductor wafer (e.g. precision wafer) is required to allow automatic handling and must have good hermetic sealing in order to prevent contamination of the precision wafer. Synthetic resin material constituting the wafer storage container is selected in order to minimize as much as possible effects of outgassing or elution of ions from the synthetic plastic material. As disclosed by Japanese Unexamined Laid-open Patent Application No. 2000-58633 JP2000-58633, synthetic resins have been used as materials suitable for such a storage container, in which the container body is a high purity polycarbonate produced using a low amount of additives and having had residual catalyst and organic solvent removed as much as possible during the material pellet production process, and in which a synthetic resin, such as polybutylene terephthalate, polyether ether ketone, or the like, has been used for the parts requiring sliding ability (e.g. parts contacting the wafer and parts for positioning against equipment).
In order to move the wafer storage container during the manufacturing process of semiconductor or shipment of semiconductor wafers, various delivery components such as side handles, a top (robotic) flange, bottom plate and a side rails, are attached to an exterior face of the container body. For those delivery components, polycarbonate has been preferably used because of its excellent properties such as moldability, dimensional stability and rigidity.
The above-described type of storage container is formed from synthetic resin that readily burns and causes increased damage when a fire occurs within a semiconductor manufacturing process while the wafer storage container is kept in storage at an in-process semiconductor manufacturing storage warehouse. In order to mitigate that problem, forming the door from a fire retardant resin, as described in Japanese Unexamined Laid-open Patent Application No. 2006-505921 (JP2006-505921), has been proposed as a countermeasure to combat this problem.
However, when the conventional wafer storage containers formed from polycarbonate resin as disclosed in JP2000-58633 and JP2006-505921 are lined up on a rack in the storage warehouse as shown in FIG. 1, the surface of the door becomes exposed at the front. Also, the robotic handle used for delivery of the wafer storage container is attached so as to protrude from the exterior wall of the top face of the container body 1, and handles used for manual delivery are attached to the left and right side walls. Thus gaps exist at the upper faces of vertically adjacent racks in order to allow insertion and removal of wafer storage containers. Gaps also exist between laterally adjacent wafer storage containers to allow insertion and removal.
Thus, if the door alone is formed from fire retardant material and the wafer storage containers are stored next to each other without gaps between adjacent wafer storage containers and also the door faces exposed at the storage rack are formed from fire retardant material, prevention of the spread of fire is possible to a certain degree. However, due to placement of delivery components such as robotic handles between vertically adjacent wafer storage containers and due to the placement of side handles between horizontally adjacent storage containers, gaps are actually present to allow insertion and removal of the wafer storage containers. When a fire occurs, the tip of the spreading flame wraps around adjacent wafer storage containers through the lateral and vertical gaps. Because the robotic handles and side handles, which are formed from readily burned synthetic resin, are present in these gaps, the fire readily spreads in the adjacent wafer storage containers. This type of wafer storage container is deficient in that this spreading of the fire causes the adjacent wafer storage containers to burn one after another.
Side rails are also provided at the side walls of the wafer container, and a bottom plate is provided at the bottom part of the wafer container. A card case holder, into which can be inserted a card case or the like for identification, is attached to the back face of the container body 1. If these side rails, the bottom plate, and the card case holder are formed from normal synthetic resin such as polycarbonate, these parts become highly combustible and promote the spread of a fire.